The hydrofoil patrol craft that never quite took off

Which naval technology or concept does Dr. Clarke wish had become more widely adopted?

Hydrofoil patrol craft, chiefly because their speed and appearance are compelling even though there is no strong operational case for retaining them.

The preference is explicitly emotional rather than a claim of superior naval utility. Hydrofoils make striking, very fast patrol craft, but their attraction does not erase the practical reasons navies moved elsewhere. Memorable technology and sustainable capability are different things.